A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. including part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Conventional lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.
A lithographic apparatus is known from U.S. Pat. No. 7,310,132 B1. In U.S. Pat. No. 7,310,132 B1 a lithographic apparatus is described including two substrate stages. Each substrate stage is provided with a long stroke module and a short stroke module which forms part of the second positioner for moving the substrate. Furthermore, the known lithographic apparatus is provided with a swap bridge in the form of a moveable member. U.S. Pat. No. 7,310,132 B1 describes two main embodiments of the known lithographic apparatus. In a first configuration the substrate stages are moveable with respect to each other, and in a second configuration, the substrate stages are coupled via the swap bridge which is realized by bringing the top surfaces of the substrate stages together by using the moveable member for a joint movement.
In a first embodiment of the known lithographic apparatus, in the first configuration, wherein substrate tables are used in parallel, or preparatory steps are carried out on one of the tables while the other table is being used for exposure, the moveable part of one of the short stroke modules carries the swap bridge. Carrying the swap bridge is undesirable as it may create a dynamical disturbance and therefore a decreased positioning accuracy since the mass of the swap bridge is added to the moveable part of the short stroke module and thus deteriorates its dynamics.
In a second embodiment of the known lithographic apparatus, in the second configuration, wherein the stages are extended and perform concurrent moving, the swap bridge is coupled to the moveable parts of the short stroke modules and to the moveable part of one long stroke module of the stages. This is undesirable because there is a dynamical coupling between the moveable parts of the short stroke and the long stroke modules. As a result, dynamical disturbances from the long stroke module can be transmitted to the short stroke modules.